PROACTIVE PRECAUTION Active warming is the most effective way to prevent unplanned perioperative hypothermia.

We're all aware of the dangers of perioperative hypothermia, and that active warming reduces complications and speeds discharges. But let's see how much you really know about the art and science of maintaining normothermia. How would you and your staff answer these 7 questions?

1. Why are surgical patients at risk?
Anesthesia impairs the body's ability to control vasoconstriction and vasodilation — the natural reflexes used to maintain core temperature — causing anesthetized patients to become poikilothermic, meaning their core temperatures are directly related to environmental conditions. Add to the mix cold OR tables, rapid air exchanges in the room that essentially create breezes blowing across patients — especially during ortho cases — and body heat that evaporates from open surgical cavities, and you've got an environment conducive to the onset of hypothermia.

2. What are the risk factors?
Some risk factors increase the potential for perioperative hypothermia, including age extremes, female gender, systolic blood pressure less than 140mmHg, higher levels of spinal blockade, normal or below-normal BMI, and history of diabetes with autonomic dysfunction.

Surgical factors that can also increase risks include longer procedures and extended time under anesthesia, a large amount of exposed body surface and certain surgical procedures: colorectal surgery, cholecystectomy, hip arthroplasty and endoscopy.

3. Which warming methods work?
Actively warming during surgery and in recovery to warm hypothermic patients is the gold standard. A multimodal approach to active warming is best, and there are plenty of effective options to choose from — forced-air units; underbody water-circulating mattresses; resistive heating blankets; and units that warm IV fluids, irrigations and blood. Tailor intraoperative warming interventions to individual patients and types of surgery. Assess patient positioning, incision size and surgical site location before deciding on which method is best. During abdominal cases, for example, it might be best to place forced-air blankets across the patient's arms and legs or use a warming underbody mattress to stave off hypothermia.

NICE TOUCH Warmed blankets are excellent comfort measures, but can't reverse hypothermia.

Passive interventions include warmed blankets, reflective blankets, socks, head coverings and limiting skin exposure. A warmed blanket is a passive solution that prevents patients from losing any temperature, but if they're already hypothermic, it's not going to actively warm them.

Evidence suggests pre-warming for a minimum of 30 minutes may reduce the risk of subsequent hypothermia. Clinical proof that warming patients pre-operatively prevents hypothermia is developing, but it has yet to definitively show the same level of efficacy as intraop and post-op warming. At the very least, pre-warming may help bump up core temperatures, so even when patients naturally lose heat, they won't drop into the hypothermic range.

4. Can warming prevent SSIs?
Hypothermia is associated with a higher risk of SSIs, because it causes tissue hypoxia and vasoconstriction, and compromises the body's normal immune function, which includes attacking infections through the bloodstream. According to research published in the Archives of Medical Research (tinyurl.com/ocoyt5t), incidence of SSIs increased significantly in mildly hypothermic patients who underwent colon resections.

5. Can warming also limit post-op pain?
Patient warming has not been clinically proven to reduce post-op pain. Although there haven't been studies that measure pain quantitatively in hypothermic patients, studies have shown that warmed patients are more comfortable and satisfied. It stands to reason that patients who aren't shivering in the PACU can concentrate on deep breathing, relaxation and imagery — factors that can help them better manage pain.

6. Do warmed patients recover faster?
Patients who are hypothermic stay in the PACU longer, which increases the cost of care. As mentioned, hypothermic patients are at greater risk for SSIs, which could prolong their overall length of stay in the inpatient setting.

Hypothermia can prolong and alter drug effects, which could impact how anesthetics work and how well post-op pain is controlled. Research (tinyurl.com/qheylol) has shown that a 3 ?C decrease in core hypothermia prolonged the effects of propofol, which could also delay discharge.

Researchers at the University of California, San Francisco, discovered that the post-op temperatures of patients who were warmed to maintain normothermia during elective abdominal surgeries had core temperatures 2 ?C higher than patients who were not warmed (tinyurl.com/og34o7e). Importantly, the researchers noted normothermic patients were cleared for discharge approximately 40 minutes earlier than hypothermic patients.

7. How common is hypothermia?
The incidence of unplanned perioperative hypothermia ranges from 20% to 40% of surgical patients. There is some preliminary research that indicates the incidence in ambulatory surgery patients may be significantly lower, and that higher preoperative temperatures may be protective of hypothermia, but further study is indicated.